Electrowetting display devices are known, for example from international patent application no. WO 2003/071346. In an off state of such a display device an oil covers the area of a pixel of the display. In an on state the oil is retracted so as not to cover the pixel area. To switch the pixel into the on state a voltage is applied across the oil via an electrically conductive fluid immiscible with the oil, which exerts an electrostatic force on the conductive fluid, and to switch the pixel into the off state the voltage is switched off. Thus, for example, where the oil is coloured, a radiation beam passing through the pixel when in the off state passes through the oil and is imparted with colour, but does not pass through the oil with the pixel in the on state and so its colour remains substantially unchanged.
The oil may be coloured using a dye. The colour of the dye may however fade over a period of time, due to prolonged exposure to radiation such as ultra violet radiation. This process is known as photo-bleaching. Consequently, the colour imparted into the radiation beam passing through the pixel changes and/or becomes weaker over time from that desired. The display device therefore provides over time an increasingly deteriorated image to a viewer.
It is an object of the present invention to reduce this disadvantage.